1. Field of the Invention
The present invention relates to an apparatus and method for controlling a fan motor of an air conditioner, and more particularly, to an apparatus and method for controlling a fan motor of an air conditioner capable of driving an outdoor fan with using a hybrid induction motor (HIM), and capable of restoring a positive temperature coefficient (PTC) of the HIM to a normal state at the time of a breakdown occurrence by cutting off power supplied to the HIM.
2. Description of the Background Art
In general, a single-phase induction motor is widely used as a fan motor of an air conditioner due to a low cost.
However, since the single-phase induction motor has a low efficiency, research to improve efficiency of the fan motor by controlling power of the air conditioner is being performed
Accordingly, a brushless direct current (BLDC) motor driven by a microcomputer is being used as the fan motor of the air conditioner.
However, the BLDC motor requires a driving circuit thus to cause a high cost.
To solve the problem, a hybrid induction motor (HIM) of a high efficiency is being used as the fan motor of the air conditioner.
FIG. 1 is a sectional view showing a hybrid induction motor (HIM) in accordance with the conventional art, and FIG. 2 is a partial planar view showing a stator core of FIG. 1.
As shown, the HIM comprises a stator 10, a squirrel type rotor 30 disposed in the stator 10 so as to be rotatable centering around a rotation shaft 31, and a permanent magnet rotor 40 disposed between the stator 10 and the squirrel type rotor 30 so as to be rotatable centering around the rotation shaft 31.
The squirrel type rotor 30 includes a rotor core 35 formed of a plurality of steel plates 36 insulation-laminated together, and a plurality of conductive bars 37 penetratingly-formed at the rotor core 35 in a circumferential direction of the rotor core 35 with an interval therebetween by a die casting method.
The permanent magnet rotor 40 includes a permanent magnet 43 having a circular shape or a cylindrical shape, and arranged at a circumferential portion of the squirrel type rotor 30 so that an S-pole and an N-pole may be alternately implemented; and a magnet supporting member 44 having one end free-rotatably coupled to the rotation shaft 31 and another end coupled to the permanent magnet 43, for supporting the permanent magnet 43.
The stator 10 includes a stator core 11 formed of a plurality of steel plates 13 insulation-laminated together, each steel plate having a disc shape and having a plurality of slots 14c of the same size W in a circumferential direction thereof; a stator coil 21 wound on the stator core 11; and a protecting portion 50 formed at a circumferential portion of the stator coil 21 by a molding method. A shaft supporting bracket 52 having a bearing 54 so as to rotatably support the rotation shaft 31 is integrally coupled to both sides of the protecting portion 50.
Each of the steel plates 13 of the stator core 11 includes a ring-shaped yoke 14a; and a plurality of teeth 14b protruding from an inner side of the yoke 14a towards the center of the steel plate in a radial direction, and having a constant interval therebetween so that a slot 14c of the same size W may be formed therebetween in a circumferential direction. The stator coil 21 has a main coil 22 and a sub coil 24 wound on each slot 14c and having different phases from each other.
FIG. 3 a schematic view showing a configuration of an air conditioner having the HIM.
As shown, the HIM is applied to an outdoor fan, and is rotated by a driving circuit.
A controlling unit 1 controls supply of cooling air by detecting an indoor temperature.
FIG. 4 is a view showing a driving circuit of the HIM.
Referring to FIG. 4, when power is supplied to the HIM, a rotating magnetic field is generated by a current flowing on a main winding coil (ML), a subsidiary winding coil (SL), and a starting capacitor (Cs).
When the rotating magnetic field is generated by the current flowing on the subsidiary winding coil (SL), a synchronous rotor is synchronized and then rotates at a synchronous speed.
By the synchronous rotor implemented as a magnet, a rotating magnetic field having an intensive flux is generated and thereby an induction rotor rotates.
A positive temperature coefficient (PTC) of the HIM is turned off as a certain time lapses.
By the current flowing on the main winding coil (ML), the subsidiary winding coil (SL), and a driving capacitor (Cr), the induction rotor is rotated.
When the induction rotor rotates, a rotational force of the induction rotor is transmitted to the air conditioner through the rotation shaft.
In case that a fan is coupled to the rotation shaft, the fan generates an air flow while being rotated.
FIG. 5 is a circuit view showing a configuration of a speed varying apparatus of the HIM.
Referring to FIG. 5, the speed varying apparatus of the HIM includes a main coil (ML), a first speed varying coil (VL1), and a second speed varying coil (VL2); first and second switches SW1 and SW2 for selecting the main coil (ML), the first speed varying coil (VL1), and the second speed varying coil (VL2) by a control signal; and a control unit 100 for outputting a control signal to vary a speed of the HIM by a user's command.
The controlling unit 100 analyzes a command inputted from outside, and outputs a control signal to control the first and second switches SW1 and SW2 based on the analysis result.
The first and second switches SW1 and SW2 are respectively switched by the control signal, and a speed of the HIM is varied by changing the number of windings of the coil.
The more the number of windings of the coil is increased, the HIM is operated at a low speed.
For instance, when a user inputs a command to operate the HIM with a high speed, the controlling unit 100 outputs a control signal so that only the main coil (ML) may be selected. Accordingly, the first and second switches SW1 and SW2 are switched, and the HIM rotates at a high speed by the current flowing on the main winding coil (ML), the subsidiary winding coil (SL), and the driving capacitor (Cr).
When the HIM is to be operated at a low speed, the current flowing on the main coil (ML), the first and second speed varying coils (VL1, VL2), and the driving capacitor (Cr) is applied to the HIM.
When the HIM is to be operated at a middle speed, the current flowing on the main coil (ML), the first speed varying coil (VL1), and the driving capacitor (Cr) is applied to the HIM.
When the HIM is coupled to an outdoor fan of the air conditioner, the outdoor fan generates an air flow while being rotated. Accordingly, warm air is discharged outward.
However, the HIM applied to the outdoor fan causes breakdown when backwind or a low voltage is applied thereto from outside. The PTC of the HIM is not restored to the original state (normal state) even if the backwind or the low voltage is removed.
Accordingly, the air conditioner is not re-started thus to have a low reliability.